Injecting Doctrine Entity into Symfony controller based on route parameters - php

Question

I want to inject Doctrine entities into controller actions based on the route parameters in an attempt to reduce the insane amount of code duplication inside my controllers.
For example I have the following route
product:
path: /product/edit/{productId}
defaults: { _controller: ExampleBundle:Product:edit }
Instead of my current approach
public function editAction($productId)
{
$manager = $this->getDoctrine()->getManager();
$product = $manager->getRepository('ExampleBundle:Product')
->findOneByProductId($productId);
if (!$product) {
$this->addFlash('error', 'Selected product does not exist');
return $this->redirect($this->generateUrl('products'));
}
// ...
}
I'd like this to be handled else where as it's repeated in at least 6 controller actions currently. So it would be more along the lines of
public function editAction(Product $product)
{
// ...
}
It seems this has in fact been done before and the best example I can find is done by the SensioFrameworkBundle http://symfony.com/doc/current/bundles/SensioFrameworkExtraBundle/annotations/converters.html
I'd use this but were not using annotations in our Symfony projects so need to look at alternatives. Any suggestions on how this can be achieved?

Answer 1

If you read the docs carefully, you'll learn that param converters actually work without annotations:
To detect which converter is run on a parameter the following process is run:
If an explicit converter choice was made with #ParamConverter(converter="name") the converter with the given name is chosen.
Otherwise all registered parameter converters are iterated by priority. The supports() method is invoked to check if a param converter can convert the request into the required parameter. If it returns true the param converter is invoked.
In other words if you don't specify a param converter in an annotation, Symfony will iterate through all registered converters and find the most appropriate one to handle your argument (based on a type hint).
I prefer to put an annotation in order to:
be explicit
save some processing time